Difference-in-differences (DiD) with 3 treatment states

I was wondering how I would adjust my model where there would be 3 treatment states. There is the untreated but the treated is split into longer treated or less treated. What I mean by this is that the treatment occurs in the 6th year and continued into the 7th year. But there is another type of treatment in which it was introduced in the 7th year. My original model was: This is showing that there were only two treatment states: treated and untreated. The data is for 7 years and of which the treatment occurs in the 6th and 7th years. I am wondering how I would change this so that there are now three treatment groups: untreated, longer treated, and less treated. Here, the treatment occurs in the 6th year and continues for some individuals. And, for other individuals, the treatment occurs in the 7th year. Currently, I wrote out: Where U is for the untreated, LO stands for being treated for longer, so in the 6th and 7th years, and then LE standard for being treated for less, so only in the 7th year. Would appreciate any help! Thank you